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Re: Rolling, Static, and Kinetic Friction




It is said: "A difference, to be a difference, must make a difference."
Since the dynamical effect is the same for rolling, static, and sliding
friction, why distinguish among them at all for the high school student?

Leigh

The reason I see to introduce the terms static and kinetic friction is to
account for the differences in their respective coefficients. It is true
that each forces operates in an identical fashion, but a distinction must
be made to account for the difference! Inertial and adhesion are nicely
introduced in this lecture, with the aid of cohesion plates and by
lifting a lab table with a calculator on it until it just moves. If the
angle is maintained, the calculator (with little rubber feet-TI81
variety) clearly accelerates. To maintain constant speed, the table must
be lowered to an obiously lower angle. It is also noce to try this
demonstration with a tape dispensor, with its very "sticky" rubber base,
angles approaching 65+ degrees are achieved.



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TK McCarthy, PhD Email:mcca6300@spacelink.msfc.nasa.gov